glibc 2.23 is now in Debian unstable, making us unable to build the gmt package.

The bugreport in Debian has been raised to Release Critical severity which will cause the automatic removal of the affected gmt package from testing (where the next stable release is prepared) in 30 days.

I prefer to include a patch with the fix(es) for the glibc 2.23 build failure to prevent the automatic removal, because the next GMT release is not expected until a few weeks from now.